.\" $OpenBSD: SSL_CTX_set_default_passwd_cb.3,v 1.9 2023/09/19 09:40:35 schwarze Exp $
.\" full merge up to: OpenSSL 9b86974e Aug 17 15:21:33 2015 -0400
.\" selective merge up to: OpenSSL 18bad535 Apr 9 15:13:55 2019 +0100
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.Dd $Mdocdate: September 19 2023 $
.Dt SSL_CTX_SET_DEFAULT_PASSWD_CB 3
.Os
.Sh NAME
.Nm SSL_CTX_set_default_passwd_cb ,
.Nm SSL_CTX_set_default_passwd_cb_userdata ,
.Nm SSL_CTX_get_default_passwd_cb ,
.Nm SSL_CTX_get_default_passwd_cb_userdata
.Nd set or get passwd callback for encrypted PEM file handling
.Sh SYNOPSIS
.In openssl/ssl.h
.Ft void
.Fn SSL_CTX_set_default_passwd_cb "SSL_CTX *ctx" "pem_password_cb *cb"
.Ft void
.Fn SSL_CTX_set_default_passwd_cb_userdata "SSL_CTX *ctx" "void *userdata"
.Ft pem_password_cb *
.Fn SSL_CTX_get_default_passwd_cb "SSL_CTX *ctx"
.Ft void *
.Fn SSL_CTX_get_default_passwd_cb_userdata "SSL_CTX *ctx"
.Sh DESCRIPTION
.Fn SSL_CTX_set_default_passwd_cb
sets the password callback for loading a certificate or private key
from encrypted PEM format.
In particular, the callback is used by
.Xr SSL_CTX_use_certificate_file 3 ,
.Xr SSL_use_certificate_file 3 ,
.Xr SSL_CTX_use_certificate_chain_file 3 ,
.Xr SSL_use_certificate_chain_file 3 ,
.Xr SSL_CTX_use_certificate_chain_mem 3 ,
.Xr SSL_CTX_use_PrivateKey_file 3 ,
.Xr SSL_use_PrivateKey_file 3 ,
.Xr SSL_CTX_use_RSAPrivateKey_file 3 ,
and
.Xr SSL_use_RSAPrivateKey_file 3 .
.Pp
The function pointer type of the
.Fa cb
argument is documented in the
.Xr pem_password_cb 3
manual page.
If
.Fn SSL_CTX_set_default_passwd_cb
is not called on
.Fa ctx
or if it is called with a
.Fa cb
argument of
.Dv NULL ,
.Xr PEM_def_callback 3
is used instead.
.Pp
.Fn SSL_CTX_set_default_passwd_cb_userdata
sets a pointer to the
.Fa userdata
which will be provided to the password callback on invocation.
.Pp
Since the
.Fa cb
passed to
.Fn SSL_CTX_set_default_passwd_cb
will only be used for reading and decryption and not for writing and
encryption, the library will only call it with a
.Fa verify
argument of 0.
.Pp
If an application program only needs to read and decrypt
one single private key, it can be practical to have the
callback handle the password dialog interactively.
This happens by default if neither
.Fn SSL_CTX_set_default_passwd_cb
nor
.Fn SSL_CTX_set_default_passwd_cb_userdata
is called.
In that case, the library uses
.Xr PEM_def_callback 3
with a
.Fa userdata
argument of
.Dv NULL .
.Pp
If several keys have to be handled, it can be practical
to ask for the password once, for example using
.Xr UI_UTIL_read_pw_string 3 ,
then keep it in memory and use it several times by passing a pointer to it to
.Fn SSL_CTX_set_default_passwd_cb_userdata .
.Xr PEM_def_callback 3
is able to handle this case, too, so calling
.Fn SSL_CTX_set_default_passwd_cb
is not needed in this case either.
.Pp
Other items in PEM formatting (certificates) can also be encrypted; it is
however atypical, as certificate information is considered public.
.Sh RETURN VALUES
.Fn SSL_CTX_get_default_passwd_cb
returns a function pointer to the password callback currently set in
.Fa ctx ,
or
.Dv NULL
if none is set.
.Pp
.Fn SSL_CTX_get_default_passwd_cb_userdata
returns a pointer to the userdata currently set in
.Fa ctx ,
or
.Dv NULL
if none is set.
.Sh EXAMPLES
The following example provides a subset of the functionality of
.Xr PEM_def_callback 3 ,
except that
.Xr PEM_def_callback 3
does not NUL-terminate and copies up to
.Fa size
rather than
.Fa size No \- 1
bytes.
It interprets
.Fa userdata
as a NUL-terminated string and copies it to the
.Fa password
buffer, truncating the copy if it does not fit.
.Bd -literal
int
trivial_passwd_cb(char *password, int size, int verify, void *userdata)
{
	strlcpy(password, userdata, size);
	return strlen(password);
}
.Ed
.Sh SEE ALSO
.Xr pem_password_cb 3 ,
.Xr ssl 3 ,
.Xr SSL_CTX_use_certificate 3
.Sh HISTORY
.Fn SSL_CTX_set_default_passwd_cb
first appeared in SSLeay 0.6.2 and has been available since
.Ox 2.4 .
.Pp
.Fn SSL_CTX_set_default_passwd_cb_userdata
first appeared in OpenSSL 0.9.4 and has been available since
.Ox 2.6 .
.Pp
.Fn SSL_CTX_get_default_passwd_cb
and
.Fn SSL_CTX_get_default_passwd_cb_userdata
first appeared in OpenSSL 1.1.0 and have been available since
.Ox 6.3 .
